This invention relates to a classifier and more particularly to a rotary classifier formed by a plurality of aligned, spaced rings for sorting or grading wood chips. Classifiers are useful in the paper making art wherein it is often desireable to sort or grade wood chips into different sizes, with each size corresponding to different effects on the paper making process. Each size classification will itself be, in practice, a range of sizes. While wood chip rotary classifiers for size sorting are known, they are relatively expensive. Wood chips typically are of irregular shape with some also being significantly longer than others. Most of the rotary classifiers of the plural ring type are defined by a series of parallel, apertured discs, or rings, with the product to be classified fed into one end of the drum-like structure defined by the rings. When the chips to be classified are all substantially spherical or cubical, no particular problem arises. Namely, all of the substantially spherical or cubical chips whose maximum dimension is less than the interdisc spacing will fall through the spaces between the discs. When, however, the chips include some which are elongated, there arise occasions wherein the interdisc spacing is spanned by one or more of such elongated chips whose volume is such that they should, desireably, fall between the disc spacing. This spanning behavior of elongated chips results in a less than maximum efficiency of classification, with the result that after the initial classifying step, some of the smaller (but elongated) chips remain in the classifying apparatus and pass on to the next classifying stage, where they may then pass through the next stage interdisc openings and become comingled with larger volume wood chips.